Developments over the past few years have revealed the remarkable versatility of RNA in any compartment of the cell, tasks that had been thought to be exclusively in the realm of proteins and even beyond. The chapters in this book written by leading investigators in the field provide insight into various promising avenues where RNA and nucleic acid derivatives including antisense RNAs, such as siRNA, miRNAs, amplification/selection (SELEX) generated aptamers as well as ribozymes are at the threshold of impacting medicine.